<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>后盾人</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }

        body {
            width: 100vw;
            height: 100vh;
            background: #2c3e50;
            display: grid;
        }

        ul {
            list-style: none;
            width: 400px;
            height: 100px;
            align-self: center;
            justify-self: center;
            display: grid;
            grid-template: 1fr/repeat(4, 1fr);
        }

        li {
            width: 100px;
            height: 100px;
            border-radius: 50%;
            background: #e67e22;

            display: grid;
            align-items: center;
            justify-items: center;
            /* animation-name: ;
            animation-duration: 0ms;
            animation-timing-function: ;
            animation-direction: ;
            animation-iteration-count: ;
            animation-fill-mode: ;
            animation-delay:  */
            /* animation-duration: 2s; */
            /* animation-delay: 2s; */
        }

        li:nth-child(1) {
            animation: hd 2s 2s;
        }

        li:nth-child(2) {
            /* animation-name: hd;
            animation-fill-mode: backwards; */
            animation: hd backwards 2s 2s;
        }

        li:nth-child(3) {
            /* animation-name: hd;
            animation-fill-mode: forwards; */
            animation: hd forwards 2s 2s;
        }

        li:nth-child(4) {
            /* animation-name: hd;
            animation-fill-mode: both; */
            animation: hd both 2s 2s;
        }

        @keyframes hd {
            from {
                transform: scale(0);
            }

            to {
                transform: scale(1);
                background: #2ecc71;
            }
        }
    </style>
</head>

<body>
    <ul>
        <li>normal</li>
        <li>backwards</li>
        <li>forwards</li>
        <li>both</li>
    </ul>
</body>

</html>